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Cervical dystonia is the most common form of dystonia encountered in a movement disorders clinic. Botulinum toxin has been a long-established first line therapy. Several studies, including nearly two dozen randomized clinical trials, have shown that botulinum toxin is safe and effective in reducing the clinical severity of cervical dystonia. Longitudinal data have demonstrated decades of sustained benefit and safety. Although there is a potential for the development of botulinum toxin immunoresistance, this is quite rare, and partly determined by frequency of administration, cumulative dosage, and properties of the injected product. When immunoresistance does occur, switching to an alternative type of botulinum toxin (e.g., from type A to type B) usually restores the efficacy. In this evidence-based review we highlight the results of published double blind, placebo-controlled studies. We also briefly discuss injection techniques and some unmet needs, such as the development of practical assays to detect immunoresistance and longer-acting formulations of botulinum toxin.